Evaluation of Back-Beveled and Counterbore-Tapered Joints in Energy Pipelines

2016 ◽  
Author(s):  
Xiaotong Huo ◽  
Shawn Kenny ◽  
Amgad Hussein ◽  
Michael Martens
Keyword(s):  
Stress Concentration ◽  
Wall Thickness ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Mechanical Performance ◽  
Pipe Diameter ◽  
Burst Pressure ◽  
Parameter Study ◽  
Stress Concentrations ◽  
Axial Forces

Wall thickness transition joints are used to connect energy pipeline segments; such as straight pipe to fittings with different wall thicknesses. The transition joint may be subject to axial forces and bending moments that may result in a stress concentration across the transition weld and may exceed stress based design criteria. Current engineering practices, such as CSA Z662, ASME B31.4, and ASME B31.8, recommend the use of back-bevel transition welded connections. An alternative transition weld configuration is the counterbore-taper design that is intended to reduce the stress concentration across the transition. In this study, the relative mechanical performance of these two transition design options (i.e., back-bevel and counterbore-taper) is examined with respect to the limiting burst pressure and effect of stress concentrations due to applied loads. The assessment is conducted through numerical parameter study using 3D continuum finite element methods. The numerical modelling procedures are developed using Abaqus/Standard. The performance of continuum brick elements (C3D8I, C3D8RH, C3D20R) and shell element (S4R) are evaluated. The continuum brick element (C3D8RI) was the most effective in terms of computational requirements and predictive qualities. The burst pressure limits of the transition weld designs were evaluated through a parameter study examining the significance of pipe diameter to wall thickness ratio (D/t), wall thickness mismatch ratio (t2/t1), material Grade 415 and Grade 483 and end-cap boundary condition effects. The limit load analysis indicated the burst pressure was effectively the same for both transition weld designs. The effect of pipe diameter, D/t, t2/t1, and counterbore length on the stress concentration factor, for each transition weld design, was also assessed. The results demonstrate the improved performance of the counterbore-taper weld transition; relative to the back-bevel design as recommended by current practice, through the relative decrease in the stress concentration factor. The minimum counterbore length was found to be consistent with company recommended practices and related to the pipe diameter and wall thickness mismatch.

Pipe Joint Management for Risers and Pipelines

2021 ◽  
Author(s):  
Ghiath (Guy) Mansour
Keyword(s):  
Fatigue Strength ◽  
Stress Concentration ◽  
Software Development ◽  
Wall Thickness ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Joint Management ◽  
Pipe Joints ◽  
Best Fit ◽  
Pipe Joint

Abstract Minimizing the stress concentration factor (SCF) in pipe joint welding subjected to fatigue is a major concern. Machining the joint ends is one way to achieve this. However, this adds cost, time, risk of potential crack starters, and loss of wall thickness which is detrimental for fatigue, strength, and engineering criticality assessment (ECA) in particular. Pipe joint sorting (certain joints in sequence) and end matching (rotating the pipe joints for best fit) are other ways. However, this adds time, costly logistics, risk of errors, and does not guarantee the minimum possible SCF is achieved. In a typical project, more pipe joints are procured than required in order to mitigate contingencies. For pipelines, this overage is typically a percentage of the required number of joints or pipeline length. For risers, typically double the required number of joints is procured where half of the joints is sent offshore for installation and the remaining half is kept onshore for a spare riser. Then, it becomes very important to send for installation the best pipe joints that produce the best (lowest) SCFs out of the entire batch of pipe joints. This requires calculating the SCF for every potential match of any random joints to be welded together, and then choosing the best joints. Performing such calculations by spreadsheet is not feasible considering the tremendous number of required iterations and calculations. A pipe joint management software development is presented herein which accomplishes this task and examples provided to illustrate the benefits. Note: Selecting pipe joints with the best end measurements, whether ID, OD, OOR, or thickness does not guarantee that the minimum possible SCFs will be achieved since the SCF is a function of all those measurements.

Effect of Blend Radius on Stress Concentration Factor of Crossbored Holes in Thick Walled Pressure Vessels

2003 ◽  
Author(s):  
Daniel T. Peters
Keyword(s):  
Stress Concentration ◽  
Detailed Analysis ◽  
Computer Technology ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Pressure Vessels ◽  
Stress Concentrations ◽  
The Past ◽  
Recent Developments ◽  
Fea Analysis

Many studies have been performed on the effect of stress concentration factor in thick walled cylinders caused by holes drilled to the wall perpendicular to the vessel ID, commonly called crossbores. Recent developments in FEA analysis and computer technology have allowed detailed analysis in their effect on the stresses in pressure vessels. This allows the reevaluation of many theories developed in the past. The following is a study of how applying a blend radius to the inside intersection of a vessel bore and a crossbore affects the stresses in vicinity of the hole and the stress concentrations developed near the hole.

Mechanical Properties on the Welded Connection of Pipe and Hollow Spheres Joints

2011 ◽  
Vol 189-193 ◽  
pp. 3452-3457
Author(s):  
Ya Jie Yan ◽  
Hong Gang Lei ◽  
Xue Yang
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Stress Distribution ◽  
Wall Thickness ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Hollow Spheres ◽  
Steel Structures ◽  
Element Analysis ◽  
Static Tests

Taking pipe - hollow spherical node as the object, and using ANSYS finite element analysis software, established five kinds of finite element model to analyze the stress concentration at the weld connection of the different connections of steel structures - hollow ball under the uniaxial tension. Obtained this node’s stress concentration factor, stress distribution, by changing the hollow spherical diameter and wall thickness, pipe’s diameter and wall thickness, obtained the trend of the stress concentration factor under different control ball matches. Take static tests on typical structures of two specifications 6 hollow sphere nodes, get the measured stress concentration factor, and stress distribution of this node. Through comparative analysis of theoretical analysis and experimental results, show that the two rules are consistent. The research results can provide basis for improving the pipe - hollow spherical joints connecting structural.

Statistical Approach of Stress Concentration Factor (SCF) Within Pipeline Girth Welds

2014 ◽  
Author(s):  
Pierre-Louis Auvret ◽  
Antonio Carlucci ◽  
Jun Li ◽  
Kamel MCirdi
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Material Behavior ◽  
Stress Concentrations ◽  
Alignment Procedure ◽  
Fabrication Tolerances ◽  
Girth Welds ◽  
Pipe Size

Engineering design must take care of local peaks within stress field, in order to provide relevant forecast of material behavior. Within pipeline girth welds, pipe misalignment is an ordinary cause of significant stress concentrations. The matching of pipe ends depends of the quality of alignment procedure but it is also much influenced by pipe fabrication tolerances. In general, misalignment is estimated considering the maximal and minimal values of each pipe size according to pipe fabrication tolerances. But, in practice, the probability to get a such case is very low. This paper describes how to improve the calculation of stress concentration factor (SCF) through a statistical analysis of pipe dimensions. The use of actual pipe measurements is not necessary even if it provides better SCF estimation. Indeed the distribution of pipe size can be estimated through the fabrication tolerances which require acceptable capacities of the manufacturing system.

Effect of notch sensitivity on the mechanical properties of HA/PEEK functional gradient biocomposites

2016 ◽  
Vol 36 (9) ◽  
pp. 933-941 ◽  
Author(s):  
Pan Yusong ◽  
Chen Yan ◽  
Shen Qianqian ◽  
Pan Chengling
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Orthopedic Implants ◽  
Fracture Morphology ◽  
Notch Sensitivity ◽  
Stress Concentrations ◽  
Stress Strain ◽  
Functional Gradient ◽  
Strain Behavior

Abstract Biomaterials used as loading-bearing orthopedic implants usually require various excellent properties such as mechanical, bioactive and bio-tribological performances. Moreover, all of the orthopedic applications feature stress concentrations (notch sensitivity) in their design. In the present work, hydroxyapatite-reinforced polyetheretherketone functional gradient biocomposites (HA/PEEK FGBm) were successfully prepared by the layer stacking method combined with hot pressing molding technology. The effects of notch geometry on the stress-strain behavior of HA/PEEK FGBm were evaluated. The fracture morphology was investigated by scanning electron microscopy (SEM). The study of the stress-strain behavior indicated that the tensile and flexural stresses of HA/PEEK FGBm linearly increased with increasing strain under all the notch sensitivities. The fracture strain of the biocomposites decreased with increasing stress concentration factor and total HA content in the functional biocomposites. Moreover, the tensile and flexural strengths of HA/PEEK FGBm were lower than those of homogeneous HA/PEEK biocomposites. The SEM observation of the fracture micro-morphology showed that the fracture mechanism of HA/PEEK FGBm was gradually controlled by the brittle fracture process. Furthermore, both the tensile and the flexural strengths of HA/PEEK FGBm decreased with the increase in stress concentration factor and total HA content in the biocomposites.

scholarly journals New Methods for Stress Concentration Factor Calculation in Butt Welded Joints: A Comparative Study

2020 ◽  
Author(s):  
Miroslav Randic ◽  
Duško Pavletić ◽  
Marko Fabić
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Welded Joints ◽  
Concentration Factor ◽  
Computer Software ◽  
Base Material ◽  
Geometric Parameters ◽  
Stress Concentrations ◽  
Weld Toe ◽  
Toe Angle

Abstract Surface cracks in butt-welded joints usually occur in places with increased stress concentrations. The stress concentration factor (SCF) can be calculated using an empirical equation, with five geometric parameters of a butt-welded joint (thickness of the base material, toe radius, weld toe angle, weld width, and reinforcement height). However, in anindustrial environment, it is impractical and sometimes even impossible to measure all five geometric parameters with sufficient accuracy. In this study, eight experiments on butt-welded joints were performed. All samples were scanned with a 3D scanner, and the geometric sizes of the welded joints were measured using computer software. A modified empirical expression proposed by Ushirokawa and Nakayama was used to calculate the SCF; the expression was adjusted in such a way that the SCF was calculated by knowing only the toe radius. In addition, four new expressions were proposed for the calculation of the SCF by knowing the toe radius in relation to the weld toe angle; the expressions were then compared and analysed. Additionally, the values of the stress concentrations in the butt-welded joints were obtained using afinite element method (FEM). The SCFs calculated using the four methods were compared and further discussed. Our data suggested a new accurate and straightforward approach for calculating the SCF by knowing only the weld toe radius.

Notcheffect on J and Amplification of Anisotropic Stress Concentration Factor in a Laminated Plate Subjected to Tensile Load

2015 ◽  
Vol 1105 ◽  
pp. 381-385
Author(s):  
Djamel Ouinas ◽  
Bel Abbès Bachir Bouiadjra ◽  
A. Albedah ◽  
Mohamed Sahnoun
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Fibre Orientation ◽  
Notch Root ◽  
Tensile Load ◽  
Homogeneous Material ◽  
Laminated Plate ◽  
Stress Concentrations ◽  
Anisotropic Stress

Several analytical, numerical and experimental techniques are available to study the stress concentration around the notches. The stress distribution in a rectangular composite laminated plate with a central notch was studied using the finite element method. The objective of this study is to analyze the fibre orientation effect on the variation of stress concentrations at the notch root and the J-integral at the crack-tip emanating from this notch in a plate subjected to tensile loading. The results show that the anisotropic stress concentration factor can be higher or lower than that of a homogeneous material. The area of maximum normal and tangential stresses could shift with fibre orientation with respect to the loading axis. The interaction effect between a crack located on the ligament of the plate and the circular notch of radius is considered.The results indicate that fold sequence influences appreciably the acceleration or the retardation of the crack propagation.

Mechanical Integrity Evaluation of Unequal Wall Thickness Transition Joints in Transmission Pipeline

2014 ◽  
Author(s):  
Xiaotong Huo ◽  
Shawn Kenny ◽  
Michael Martens
Keyword(s):  
Wall Thickness ◽  
Mechanical Performance ◽  
Numerical Study ◽  
Design Method ◽  
Welding Process ◽  
Process Efficiency ◽  
Parameter Study ◽  
Stress Concentrations ◽  
Joint Design ◽  
Taper Joint

Transition welds joining pipe segments of unequal wall thickness are typically designed using back-bevel butt welds in accordance with industry recommended practices. An alternative approach, for joining transition pieces, would be the use of a counterbore-taper design, which has been successively utilized by TransCanada PipeLines. In comparison with the back-bevel joint design, the counterbore-taper design provides a simple geometry that facilitates the welding process for joints of unequal wall thickness, improves the NDT quality and reliability, and increases the process efficiency for welding and NDT tasks. The counterbore-taper design reduces the effect of stress concentrations at the weldment and enhances fatigue life. A parameter study, using continuum based finite element methods, was conducted to comparatively examine the mechanical performance of a pipe joint, using back-bevel and counterbore-taper designs, with unequal wall thickness and different material grade. The parameters examined include pipe diameter, D/t ratio, axial force and moment. The numerical study assessed the mechanical stress response, including stress path, initial yield and onset of plastic collapse, for back-bevel and counterbore-taper joint designs. Based on these preliminary investigations, the performance of each transition joint design was evaluated and guidance on the selection of the joints design method was provided.

scholarly journals Stress concentrations at an oblique hole in a thick plate

2000 ◽  
Vol 35 (2) ◽  
pp. 143-147 ◽  
Author(s):  
P Stanley ◽  
A G Starr
Keyword(s):  
Stress Concentration ◽  
Flat Plate ◽  
Uniaxial Tension ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Thick Plate ◽  
Empirical Equation ◽  
Elastic Stress ◽  
Cylindrical Hole ◽  
Stress Concentrations

An empirical equation has been obtained for the elastic stress concentration factor at an isolated oblique circular-cylindrical hole in a thick flat plate subjected to a uniform, arbitrarily oriented uniaxial tension. The equation is presented and its development is outlined in this note.

scholarly journals Evaluation of the Stress Concentration Factor in Butt Welded Joints: A Comparative Study

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 411
Author(s):  
Miroslav Randić ◽  
Duško Pavletić ◽  
Marko Fabić
Keyword(s):  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Welded Joints ◽  
Concentration Factor ◽  
Computer Software ◽  
Base Material ◽  
Geometric Parameters ◽  
Stress Concentrations ◽  
Weld Toe ◽  
Toe Angle

Surface cracks in butt-welded joints usually occur in places with increased stress concentrations. The stress concentration factor (SCF) can be calculated using an empirical equation, with five geometric parameters of a butt-welded joint (thickness of the base material, toe radius, weld toe angle, weld width, and reinforcement height). However, in an industrial environment, it is impractical and sometimes even impossible to measure all five geometric parameters with sufficient accuracy. In this study, eight experiments on butt-welded joints were performed. All samples were scanned with a 3D scanner, and the geometric sizes of the welded joints were measured using computer software. A modified empirical expression proposed by Ushirokawa and Nakayama was used to calculate the SCF; the expression was adjusted in such a way that the SCF was calculated by knowing only the toe radius. In addition, four new expressions were proposed for the calculation of the SCF by knowing the toe radius in relation to the weld toe angle; the expressions were then compared and analyzed. Additionally, the values of the stress concentrations in the butt-welded joints were obtained using a finite element method (FEM). The SCFs calculated using the four methods were compared and further discussed. Our data suggested a new accurate and straightforward approach for calculating the SCF by knowing only the weld toe radius.

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